Idealista.com, Spain's biggest real estate portal has gathered together all of the Bank Repossessions on one page.  It lets you search by province or by Bank.  As far as I can see, it has all of the main banks and cajas' repossessions.

Currently there are 56, 544 bank and caja repossessions on idealista.com.  Unfortunately, the website is in Spanish, so you will need to know at least some Spanish.

Here's the link:

http://www.idealista.com/pagina/pisos-bancos